Reflector which exhibits good reflectance over wide angle range and liquid crystal display using the same

ABSTRACT

Light-reflective concave portions are disposed on the surface of a substrate. The concave portions have a first and second vertical section perpendicular to each other. The first vertical section has an internal shape defined by a first curve and a second curve, the first curve extending from one point on the peripheral edge of the concave portion to the deepest point of the concave portion, and the second curve extending continuously from the first curve and from the deepest point of the concave portion to another point on the peripheral edge of the concave portion. The average of the absolute value of an inclination angle of the first curve is larger than that of the second curve relative to the substrate surface. The second vertical section has an internal shape defined by a shallow curve and deep curves formed at both sides of the shallow curve.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to reflectors which are suitablefor use in liquid crystal displays using external light, a front light,a backlight, etc., as a light source, and to liquid crystal displaysusing the reflectors. More specifically, the present invention relatesto a reflector which exhibits good reflectance over a wide angle rangeand especially high reflectance in a reflection direction in a desiredrange, and to a liquid crystal display which uses the reflector so thatit has a wide viewing angle and exhibits moderate directionality suchthat the display appears sufficiently bright when seen from a typicalviewing area.

[0003] 2. Description of the Related Art

[0004] Liquid crystal displays are commonly used as display units formobile computers, etc., and reflective liquid crystal displays, whichuse external light as a light source, are one kind of liquid crystaldisplays which are commonly used because of their low power consumption.In addition, liquid crystal displays having a front light for obtainingextra light in addition to external light are also commonly used.

[0005] In such liquid crystal displays, external light incident on thedisplay surface (from the observer side) or light emitted from a frontlight is reflected by a reflector and is emitted outside the displaysurface, so that a user can view an image which changes in accordancewith the alignments of liquid crystal molecules in a liquid crystallayer.

[0006] In addition, liquid crystal displays having a backlight forobtaining extra light in addition to external light are also commonlyused. In liquid crystal displays having a backlight, a semi-transmissivereflector is used in order to reflect external light and to pass lightemitted from the backlight.

[0007] The inventors have performed various investigations with respectto the relationship between the shape of the surface of a reflector (theshape of the surface closer to a display surface) and reflectioncharacteristics of the reflector.

[0008] When a reflector having a flat, specular surface is used, thereflector exhibits extremely high reflectance at a specific reflectionangle determined in accordance with an incidence angle. However, areflection-angle range in which high reflectance is obtained isextremely narrow. Thus, a reflector having high directionality such thata viewing area from which the reflector appears bright is narrow isobtained. In addition, visibility is degraded due to so-called backreflection, that is, reflection of a light source, an observer's face,etc. in a display surface.

[0009] Accordingly, several techniques have been suggested in whichconcave portions having shapes like parts of a sphere, grooves, orirregular concavities and convexities are formed over the surface of areflector in order to obtain good reflectance over a wide range.According to these techniques, reflection characteristics can be madesuch that the reflector appears bright over a wide viewing area.

[0010]FIG. 9 shows a reflector in which a plurality of concave portionseach shaped like a part of a sphere are formed on the surface of thereflector. With reference to FIG. 9, a reflector 51 is constructed byforming a plate-shaped resin base member 53 (a base member of thereflector) made of a photosensitive resin layer, etc., on a substrate 52made of glass, etc., and forming a plurality of concave portions 54 overthe surface of the resin base member 53. The inner surfaces of theconcave portions 54 are shaped like a part of a sphere, and the concaveportions 54 are formed continuously so that the concave portions 54overlap one another. In addition, a reflective film 55 formed of a thinlayer of aluminum, silver, etc. is formed on the concave portions 54 byvapor deposition, plating, etc.

[0011] The concave portions 54 are formed such that the depth thereofvaries in the range of 0.1 μm to 3 μm, and are irregularly arranged suchthat the pitch between the concave portions 54 varies in the range of 5to 50 μm. In addition, the inner surface of each concave portion 54 isshaped like a part of a single sphere, and an inclination angle thereofis set in the range of −18° to +18°.

[0012] The term “depth of a concave portion” used herein means thedistance between the substrate surface of a reflector and the deepestpoint of a concave portion, and the term “pitch between adjacent concaveportions” used herein means the distance between the central points ofadjacent concave portions, which have a circular shape as seen in a planview. A surface as used herein is essentially a flat surface thatdisregards the minute irregularities (e.g. relatively microscopiccrevasses or projections) present in almost every physical layer. Such aflat surface includes, for example, the substrate surface in which theconcave portions are non-existent or are completely filled in.

[0013] In addition, “inclination angle” means an angle of a tangentialline at an arbitrary point on the inner surface of the concave portions54 relative to the substrate surface in a specific vertical section.

[0014] The reflector 51 has reflection characteristics similar to thoseof a comparative example (see FIG. 6), which will be described below.FIG. 6 is a graph showing the reflection characteristics in the case inwhich an incidence angle is 30°, where the vertical axis showsreflectance (reflection intensity) and the horizontal axis shows areflection angle.

[0015] With reference to FIG. 10, an incidence angle is defined as anangle ω₀ between the normal H of the reflector 51 (substrate surface)and incident light J. In addition, a reflection angle is defined as anangle ω between the normal H and reflection light K on a plane includingthe normal H and the incident light J. In addition, a specularreflection angle relative to the substrate surface is defined as anangle at which the incidence angle ω₀ and the reflection angle ω are thesame.

[0016] As shown in FIG. 6, for a specular reflection angle of 30°, thereflector 51 has a relatively good reflectance in the range of15°≦ω≦45°.

[0017] The above-described reflector 51 of the known art exhibitsrelatively good reflectance over a relatively wide angle range due tothe concave portions. However, as shown FIG. 6, reflectance at 30°,which is the specular reflection angle, is relatively low compared withtwo peaks at 15° and 45°. Accordingly, reflection characteristics of thereflector 51 are such that although relatively good reflectance isensured for a relatively wide range, brightness is reduced in thespecular reflection angle.

[0018] However, when display units installed in devices such as notebookcomputers, desk calculators, watches, etc., are viewed, the direction ofa light source (incidence angle) and a viewing angle of a user whoreceives reflection light (reflection angle) are normally in a specificrange. Accordingly, it would be more convenient for the user to providea display which not only appears bright in a wide area but also exhibitsespecially high reflection intensity in a specific direction.

[0019] In addition, in the case in which the above-described reflector,which appears bright over a wide viewing area, is used in liquid crystaldisplays having a backlight, a problem exists in that light emitted fromthe backlight is diffused too widely at the surface of the reflector andlight emitted in the specular reflection angle, which is the angle atwhich a user normally views the display, is reduced.

SUMMARY OF THE INVENTION

[0020] In order to solve the above-described problems, an object of thepresent invention is to provide a reflector which exhibits goodreflectance over a wide angle range and especially high reflectance in areflection direction in a desired range, especially in a directionshifted from a direction of specular reflection, and which preventslight emitted from a backlight from being diffused too widely. Inaddition, it is also an object of the present invention to provide areflective liquid crystal display which uses the reflector so that itappears bright over a wide viewing area and exhibits moderatedirectionality in a normal viewing area.

[0021] In order to solve the above-described problems, the presentinvention provides a reflector including a substrate having a pluralityof light-reflective concave portions on the surface thereof, eachconcave portion having a first vertical section and a second verticalsection which pass through a deepest point of the concave portion.

[0022] The first vertical section has an internal shape defined by afirst curve and a second curve, the first curve extending from one pointon the peripheral edge of the concave portion to the deepest point ofthe concave portion and the second curve extending continuously from thefirst curve from the deepest point of the concave portion to anotherpoint on the peripheral edge of the concave portion, and the average ofthe absolute value of an inclination angle of the first curve relativeto the substrate surface is larger than the average of the absolutevalue of an inclination angle of the second curve relative to thesubstrate surface.

[0023] The second vertical section is perpendicular to the firstvertical section and has an internal shape defined by a shallow curveand deep curves formed at both sides of the shallow curve, the deepcurves having a smaller radius of curvature compared with the shallowcurve.

[0024] Although the direction of the first vertical section is notdetermined, the vertical section along the up-down direction or thefront-back direction relative to an observer is preferably defined asthe first vertical direction.

[0025] As described above, in the reflector of the present invention, aplurality of light-reflective concave portions are formed on thesubstrate surface, and each of the concave portions has a curved surface(concave surface). Accordingly, the reflector appears bright from a wideviewing area and has a light-diffusing characteristic so that backreflection is suppressed.

[0026] The internal shape of each concave portion along the firstvertical section is defined by the first curve and the second curvewhich are connected to each other at the deepest point. The first andthe second curves are formed such that the average of the absolute valueof the inclination angle of the first curve relative to the substratesurface is larger than the average of the absolute value of theinclination angle of the second curve relative to the substrate surface.More specifically, the inclination of the first curve is relativelysteep and the inclination of the second curve is relatively gentle, andthe second curve is longer than the first curve.

[0027] Accordingly, the amount of light reflected by the surface atregions around the second curve is larger than the amount of lightreflected by the surface at regions around the first curve. Morespecifically, luminous flux density of reflection light in the directionof specular reflection relative to the surface at regions around thesecond curve is increased. Accordingly, when the first curves in eachconcave portion are aligned in a specific direction (or in a pluralityof specific directions), reflectance in the specific direction(s) can beincreased over the entire region of the reflector.

[0028] In addition, internal shape of each concave portion along thesecond vertical section, which is perpendicular to the first verticalsection, is defined by the shallow curve and the deep curves formed atboth sides of the shallow curve, the deep curves having a small radiusof curvature. Accordingly, reflectance in the direction of specularreflection can be increased. Preferably, the deep curves are formedsymmetrically across the shallow curve.

[0029] As a result, the overall reflection characteristics in the firstvertical section are made such that peak reflectance is obtained atabout the specular reflection angle and reflectance in the direction inwhich light is reflected by the surface at regions around the secondcurve B is increased. More specifically, reflection characteristics inwhich reflection light is moderately condensed in a specific directionwithout reducing the intensity of reflection light in the direction ofspecular reflection can be obtained.

[0030] According to the present invention, the concave portions arepreferably formed such that the first vertical sections and the secondvertical sections of each concave portion are aligned in the samedirection and the orientations of the first curves in each concaveportion are the same. More specifically, the orientations of the firstcurves in each concave portion are preferably made the same, and theorientations of the second curves in each concave portion are alsopreferably made the same.

[0031] In such a case, reflectance in the direction in which light isreflected by the surface at regions around the second curve B isincreased over the entire region of the reflector. Accordingly,reflection characteristics in which reflection light is moderatelycondensed in a specific direction can be obtained.

[0032] In addition, according to the present invention, the inclinationangle of the first curve relative to the substrate surface and theinclination angle of the second curve relative to the substrate surfaceare preferably substantially zero at the point at which the first curveand the second curve are connected to each other. In addition,preferably, when the inclination angle of the first curve is negativeand the inclination angle of the second curve is positive, theinclination angle of the first curve is gradually increased from anegative value and the inclination angle of the second curve isgradually reduced from a positive value, and both the inclination anglesof the first and second curves become substantially zero at the point atwhich the first and second curves are connected to each other.

[0033] Accordingly, the internal surfaces of each concave portion can bemade smooth over the entire regions thereof, and reflectance in thedirection of specular reflection can be prevented from being reduced.

[0034] Preferably, the concave portions are irregularly formed such thatthe depth thereof varies in the range of about 0.1 μm to 3 μm.

[0035] When the depths of the concave portions are less than about 0.1μm, sufficient light-diffusing effect cannot be obtained. When thedepths of the concave portions exceed about 3 μm, the thickness of thesubstrate, which must be larger than the depths of the concave portions,becomes too large and leads to problems in the manufacturing process anddeterioration in product quality. Further, because a moiré patternoccursdue to light interference when the concave portions are formedregularly, by forming the concave portions with various depths theemergence of a moire pattern is avoided. In addition, the reflectionlight is prevented from converging too sharply at a predeterminedviewing angle and the amount of reflection light varies smoothly in theviewing area.

[0036] Preferably, the concave portions are irregularly arranged next toeach other.

[0037] When the concave portions are formed separately, regions at whichspecular reflection occurs are increased since the regions between theconcave portions are flat, and sufficient light-diffusing effect cannotbe obtained in the limited pixel area. Accordingly, the concave portionsare preferably formed next to each other. In addition, the concaveportions are preferably formed irregularly since the moiré patternappears when the concave portions are formed regularly.

[0038] The present invention also provides a reflective liquid crystaldisplay which includes one of the above-described reflectors.Preferably, the concave portions are formed such that the first verticalsections and the second vertical sections of each concave portion arealigned in the same direction and the orientations of the first curvesin each concave portion are the same, and the reflector is installedsuch that the first curves are disposed above the second curves in eachconcave portion when viewed by an observer.

[0039] When the first curves are disposed above the second curves ineach concave portion when viewed by the observer, external light, whichis mainly incident from the upper side, can be reflected in a directionshifted toward the normal of the substrate surface from the lower sideof the observer.

[0040] In addition, since external light, which is mainly incident fromthe upper side of the observer, is efficiently received at regionsaround the second curves, the amount of reflection light is increasedover the entire region.

[0041] In addition, the amount of light reflected in the direction ofspecular reflection can be increased due to the reflection at theshallow curve in the second vertical section.

[0042] Accordingly, the amount of light reflected toward the eyes of theobserver is increased, and a reflective liquid crystal display whichappears bright from the viewpoint of the observer can be obtained.

[0043] The present invention also provides a reflector in which peakreflectance is obtained at about the specular reflection angle and anintegrated value of reflectance in a reflection-angle range smaller thana specular reflection angle with respect to the substrate surface isdifferent from an integrated value of reflectance in a reflection-anglerange larger than the specular reflection angle.

[0044] Accordingly, when a normal viewing angle of the observer isdisplaced from the direction of specular reflection relative to thesubstrate surface, a reflector in which light is mainly reflected in thedirection of the normal viewing angle without reducing the amount ofreflection light in the direction of specular reflection can beobtained.

[0045] The present invention also provides a reflective liquid crystaldisplay which includes a reflector in which peak reflectance is obtainedat about a specular reflection angle and an integrated value ofreflectance in a reflection-angle range smaller than a specularreflection angle with respect to the substrate surface is different froman integrated value of reflectance in a reflection-angle range largerthan the specular reflection angle. The reflector is installed such thatthe reflection-angle range corresponding to the larger of the integratedvalues of reflectance is disposed at the upper side of the specularreflection angle with respect to the substrate surface when viewed by anobserver.

[0046] According to the present invention, external light, which ismainly incident from the upper side, can be reflected in the directionshifted toward the normal of the substrate surface from the lower sideof the observer.

[0047] Accordingly, when the reflective liquid crystal display of thepresent invention is used as a display for a mobile phone or a notebookcomputer, the amount of light reflected toward the eyes of the observeris increased, and a reflective liquid crystal display which appearsbright from the viewpoint of the observer can be obtained.

[0048] As described above, according to the present invention, areflector can be obtained which has a light-diffusing characteristic sothat incident light is diffusely reflected and back reflection issuppressed over a wide viewing angle, and in which the amount ofreflection light in the viewing-angle range in which the observernormally views the display is increased.

[0049] In addition, in a reflective liquid crystal display containingthe reflector of the present invention, display surface appearsespecially bright when viewed in a specific viewing-angle range so thatvisibility is improved, and back reflection is suppressed over a wideviewing-angle range.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050]FIG. 1 is a perspective view of a reflector according to anembodiment of the present invention;

[0051]FIG. 2 is a perspective view of a concave portion according to theembodiment;

[0052]FIG. 3 is a sectional view of the concave portion along a firstvertical section;

[0053]FIG. 4 is a sectional view of the concave portion along a secondvertical section;

[0054]FIG. 5 is a diagram showing the reflection characteristics of areflector according to the embodiment;

[0055]FIG. 6 is a graph showing the relationship between alight-receiving angle and reflectance;

[0056]FIG. 7 is a sectional view showing the layer structure of thereflective liquid crystal display according to the embodiment;

[0057]FIG. 8 is a diagram showing a manner in which the reflectiveliquid crystal display according to the embodiment is used;

[0058]FIG. 9 is a perspective view showing a reflector of the known art;and

[0059]FIG. 10 is a diagram showing an incidence angle and a reflectionangle.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0060] An embodiment of the present invention will be described belowwith reference to the accompanying drawings; however, it is not intendedto limit the scope of the present invention.

[0061]FIG. 1 is a diagram showing a reflector 1 according to anembodiment of the present invention. As shown in FIG. 1, the reflector 1of the present embodiment is constructed of a plate-shaped substrate 2formed of, for example, aluminum. A plurality of light-reflectiveconcave portions 3 a, 3 b, 3 c, . . . , (denoted as concave portions 3when they are generically described) are irregularly formed next to eachother on the surface S (standard surface) of the substrate 2.

[0062] The internal shape of the concave portion 3 is shown in FIGS. 2to 4. FIG. 2 is a perspective view of the concave portion 3, FIG. 3 is asectional view of the concave portion 3 cut along a first verticalsection X, and FIG. 4 is a sectional view of the concave portion 3 cutalong a second vertical section Y, which is perpendicular to the firstvertical section X.

[0063] As shown in FIG. 3, the internal shape of the concave portion 3along the first vertical section X is defined by a first curve A and asecond curve B, the first curve A extending from one point S1 on theperipheral edge to the deepest point D, and the second curve B extendingcontinuously from the first curve A from the deepest point D to theother point S2 on the peripheral edge. With reference to FIG. 3, thefirst curve A extends downward toward the right, and the second curve Bextends upward toward the right. In addition, both an inclination angleof the first curve A relative to the substrate surface S and aninclination angle of the second curve B relative to the substratesurface S are substantially zero at the deepest point D, where the firstcurve A and the second curve B are smoothly connected to each other.

[0064] The inclination angle of the first curve A relative to thesubstrate surface S is steeper than the inclination angle of the secondcurve B, and the deepest point D is at a position shifted toward the xdirection from the central point O of the concave portion 3 (i.e. thedeepest point D and the central point O of the concave portion are notvertically aligned). More specifically, the average of the absolutevalue of the inclination angle of the first curve A relative to thesubstrate surface S is larger than the average of the absolute value ofthe inclination angle of the second curve B relative to the substratesurface S. The average of the absolute value of the inclination angle ofthe first curve A relative to the substrate surface S in the concaveportions 3 a, 3 b, 3 c, . . . , varies in the range of about 20 to 900.In addition, the average of the absolute value of the inclination angleof the second curve B relative to the substrate surface S in the concaveportions 3 a, 3 b, 3 c, . . . , varies in the range of about 1° to 89°.

[0065] In addition, as shown in FIG. 4, the internal shape of theconcave portion 3 along the second vertical section Y is approximatelysymmetrical about the vertical line passing through the central point Oof the concave portion 3. The region around the deepest point D isdefined by an almost linear, shallow curve E having a large radius ofcurvature, and regions at the right and left sides of the shallow curveE are defined by deep curves F and G having a small radius of curvature.In each of the concave portions 3 a, 3 b, 3 c, . . . , the absolutevalue of an inclination angle of the shallow curve E relative to thesubstrate surface S is generally about 10° or less. In addition, theabsolute values of inclination angles of the deep curves F and Grelative to the substrate surface S in the concave portions 3 a, 3 b, 3c, . . . , vary in the range of, for example, about 2° to 90°. Note thatalthough the term “each of the concave portions” is used in multipleplaces throughout the detailed description, a substantial majority ofthe concave portions may be used as well as every concave portion. Aslong as the effects described herein are achieved, the absolutepercentage of concave portions which are, for example, oriented inexactly the same direction is inconsequential.

[0066] In addition, the distance between the deepest point D and thesubstrate surface S is defined as the depth of each concave portion 3,and the depth of the concave portions 3 a, 3 b, 3 c, . . . , varies inthe range of about 0.1 μm to 3 μm.

[0067] In the present embodiment, the first vertical sections X of eachof the concave portions 3 a, 3 b, 3 c, . . . , are aligned in the samedirection. Similarly, the second vertical sections Y of each of theconcave portions 3 a, 3 b, 3 c, . . . , are aligned in the samedirection. In addition, the orientations of the first curves A in eachof the concave portions 3 a, 3 b, 3 c, . . . , are the same. Morespecifically, in every concave portion, the x axis shown in FIGS. 2 and3 extends in the same direction.

[0068] In the reflector 1 of the present embodiment, the orientations ofthe first curves A in each of the concave portions 3 a, 3 b, 3 c, . . ., are the same. Accordingly, as shown in FIG. 5, the reflectioncharacteristics of the reflector 1 are such that the reflectiondirection is shifted from the direction of specular reflection relativeto the substrate surface S.

[0069] More specifically, as shown in FIG. 5, the reflection light Kcorresponding to incident light J, which is incident at an angle fromthe upper side of the x direction, is shifted such that a viewing areafrom which the display appears bright is shifted from the direction ofspecular reflection K₀ toward the normal H relative to the substratesurface S. The angles formed by the incident light J and specularreflection K₀ are symmetric around the normal H of the substrate surfaceS.

[0070] In addition, as described above, the internal shape of eachconcave portion 3 along the second vertical section Y, which isperpendicular to the first vertical section X, is defined by the shallowcurve E having a large radius of curvature and the deep curves F and Ghaving a small radius of curvature. Accordingly, reflectance in thedirection of specular reflection relative to the substrate surface canbe increased.

[0071] As a result, as shown in FIG. 6, the overall reflectioncharacteristics in the first vertical section X are made such that peakreflectance is obtained at about the specular reflection angle andreflectance in the direction in which light is reflected by the surfaceat regions around the second curve B is increased. More specifically,reflection characteristics in which reflection light is moderatelycondensed in a specific direction without reducing the amount ofreflection light in the direction of specular reflection can beobtained.

[0072] More specifically, FIG. 6 shows the relationship between thelight-receiving angle (θ°) of a viewer and brightness (reflectance) inthe case in which external light is radiated onto the display surface ofthe reflector 1 of the present embodiment under a condition in which theincidence angle is 30°. The light-receiving angle is changed from 0°(angle corresponding to the normal) to 60° across the midpoint 30°,which is the specular reflection angle relative to the display surface(substrate surface). As a comparative example, the relationship betweenthe light-receiving angle and the reflectance in a reflective liquidcrystal display containing a known reflector having spherical concaveportions is also shown in FIG. 6.

[0073] As is apparent from FIG. 6, in the comparative example, thereflectance is approximately constant when the light receiving angle isin the range of 15° to 45° (although there is somewhat of a decrease inemission at the specular angle). In contrast, with respect to thereflector 1 of the present embodiment, peak reflectance is obtained atabout 30°, that is, about the specular reflection angle relative to thesubstrate surface S. In addition, the integrated value of thereflectance in the range in which the light-receiving angle is smallerthan the specular reflection angle (30°) is larger than the integratedvalue of the reflectance in the range in which the light-receiving islarger than the specular reflection angle. More specifically, sufficientbrightness can be obtained at viewing angles around 20° while ensuringbrightness in the direction of specular reflection. The reason for thisis that most users typically view the display (for example, incomputers, cellular telephones, watches, PDAs) at angles of about normalto the surface to about the specular reflection angle (or here a littlelarger—about 35° from normal), with angles around 20° being especiallypopular. Thus, the liquid crystal display should have increasedbrightness relative to a conventional liquid crystal display at leastfrom about normal to the surface to about the specular reflection angle.

[0074] Although the manufacturing method for the reflector 1 is notlimited, the reflector 1 can be manufactured by, for example, thefollowing processes.

[0075] First, a punch (stamping tool) having a convex end portioncorresponding to the shape of the above-described convex portions isprepared. The punch is held such that the end portion thereof opposes analuminum substrate, and is repeatedly pressed against the aluminumsubstrate so as to form the convex portions over the entire area of apredetermined region of the aluminum substrate. While the punch isrepeatedly pressed against the aluminum substrate, the orientation ofthe punch relative to the aluminum substrate is maintained constant andthe stroke and interval are changed irregularly. The stroke is adjustedsuch that the depth of the concave portion is in a predetermined range,and the interval is adjusted such that a moiré pattern does not appear.

[0076] Of course, the reflector 1, is shown as formed from a singlereflective material. In another embodiment, the reflector 1 may comprisea base portion onto which the concave portions were formed and areflective layer disposed on the base layer. The base portion may beformed in a manner similar to that of the reflector 1, above, while thereflective layer may be formed by deposition, sputtering, evaporation orany other suitable method. The base portion may be any material suitablefor forming the concave portions, organic or inorganic (for exampleglass), while the reflective layer may be, for example, a thin metalliclayer. Alternately, the base portion may be the substrate itself.

[0077]FIG. 7 is a sectional view showing the layer structure of areflective liquid crystal display 100 containing the reflector 1 of thepresent embodiment.

[0078] With reference to FIG. 7, in the reflective liquid crystaldisplay 100, a display-side substrate 20 and a reflector-side substrate10 oppose each other with a liquid crystal layer 30 therebetween. Thedisplay-side substrate 20 is transmissive and the reflector-sidesubstrate 10 is reflective. The external surface of the display-sidesubstrate 20 serves as a display surface, and the reflector-sidesubstrate 10 is provided with the reflector 1.

[0079] The reflector-side substrate 10 is formed by laminating a glasssubstrate 11, the reflector 1, a transparent intervening layer 13, acolor-filter layer 14, a transparent planarizing layer 15, a transparentelectrode layer 16 formed of an Indium Tin Oxide (ITO) film, a Nesafilm, etc., and an alignment layer 17, in that order from the bottom. Inaddition, the display-side substrate 20, which opposes thereflector-side substrate 10 across the liquid crystal layer 30, isformed by laminating an alignment layer 21, an insulating layer 22, atransparent electrode layer 23 formed of an ITO film, a Nesa film, etc.,a glass substrate 24, and a light-modulating layer 25 (a polarizingplate, a retardation plate, etc.) in that order from the liquid crystallayer 30.

[0080] Transparent electrodes of the transparent electrode layer 16 andtransparent electrodes of the transparent electrode layer 23 arearranged in striped patterns which perpendicularly cross each other, theliquid crystal layer 30 being disposed therebetween. Thus, asimple-matrix liquid crystal device is formed in which pixels are formedat intersections of the transparent electrodes of the transparentelectrode layer 16 and the transparent electrodes of the electrode layer23.

[0081] Of course, the transparent electrodes may be formed in otherpatterns and provided at different locations in the liquid crystaldisplay 100, as can the color filters in the color-filter layer 14. Forexample, the color filters may be provided in the display-side substrate20 rather than the reflector-side substrate 10, being formed on thesubstrate 24 and having another insulating layer disposed thetransparent electrode layer 23 and the color filter for instance.Examples of possible arrangements of the color filters include astripe-type arrangement having different colors arranged successivelyside by side, a delta-type arrangement having colors arranged in atriangular shape, and a mosaic-type arrangement having arrangedsuccessively side by side in a vertical direction and a horizontaldirection. In addition, the color filters may comprise different colors(red, blue, green, cyan, magenta, yellow or achromatic to name a few).

[0082] In the reflective liquid crystal display 100, the reflector 1 isaligned such that the first curves A in the concave portions 3 a, 3 b, 3c, . . . , are placed in the x direction relative to the second curvesB, which have gentler slopes. In addition, characters, etc., aredisplayed in the orientation such that the x direction is aligned withthe upward direction.

[0083]FIG. 8 is a diagram showing the manner in which the reflectiveliquid crystal display 100 is used. In FIG. 8, only the first curves Aand the second curves B in the reflective liquid crystal display 100 areshown and other components are omitted for convenience.

[0084] The reflective liquid crystal display 100 is installed in amobile phone, a notebook computer, personal data assistant, etc., in theorientation such that the x direction is aligned with the upwarddirection. In such a case, as shown in FIG. 8, the reflective liquidcrystal display 100 is normally set or held at an angle relative to thehorizontal plane such that the x direction is aligned with the upwarddirection. More specifically, when the reflective liquid crystal display100 is used, it is disposed such that the first curves A are above thesecond curves B in each concave portion when viewed by the observer. Inaddition, the observer normally looks down onto the reflective liquidcrystal display 100 from the upper side relative to the direction ofspecular reflection K₀ and from the lower side relative to thehorizontal plane.

[0085] In such a case, external light (incident light J), which isprimarily incident from the upper side, is mainly reflected by thesurface at regions around the second curves B, so that reflection lightK is not easily directed toward the lower side of the observer butrather heads essentially toward the upper side relative to the directionof specular reflection K₀.

[0086] Accordingly, the viewing area from which the observer normallyviews the display and the viewing area from which the display appearsbright are made the same. Therefore, a display which appears bright fromthe viewpoint of the observer can be obtained.

[0087] Although the reflective liquid crystal display according to thepresent embodiment shown in FIG. 7 is constructed such that thereflector 1 and the transparent electrode layer 16 are formedseparately, the transparent electrode layer 16 may also be formed of thereflector 1 and placed at the position where the reflector 1 is formedin FIG. 7. In such a case, the transparent electrode layer also servesas a reflector, and the layer structure of the reflective liquid crystaldisplay can be made simpler.

[0088] In addition, the above-described reflector may be formed of asemi-transmissive, semi-reflective substrate such as a half mirror,etc., and an illumination plate may be disposed behind the liquidcrystal panel. In such a case, a semi-transmissive, semi-reflectiveliquid crystal display can be obtained which serves as a reflective typewhen external light is bright and serves as a transmissive type byilluminating the illumination substrate when external light is dark. Forthis, the liquid crystal display may also include a light sourcedisposed under or to one side of the display and additionally include alight guide to guide the light from the light source to at least thearea under the reflector and display. The present invention may also beapplied to such semi-transmissive, semi-reflective liquid crystaldisplays.

[0089] In addition, when a front light is disposed in front of thedisplay-side substrate 20, a front-light liquid crystal display can beobtained in which external light is exclusively used when the externallight is bright and the front light is optionally used when the externallight is dark. The present invention may also be applied to suchfront-light liquid crystal displays.

[0090] The liquid-crystal driving method is not limited in the presentinvention, and the present invention may also be applied toactive-matrix liquid crystal displays using thin film transistors andthin film diodes, segmented liquid crystal displays, etc., in additionto the above-described simple-matrix liquid crystal display.

What is claimed is:
 1. A reflector comprising a substrate having aplurality of light-reflective concave portions on a surface thereof,each concave portion having a first vertical section and a secondvertical section which pass through a deepest point of the concaveportion, wherein the first vertical section has an internal shapedefined by a first curve and a second curve, the first curve extendingfrom a first point on a peripheral edge of the concave portion to thedeepest point of the concave portion, and the second curve extendingcontinuously from the first curve and from the deepest point of theconcave portion to a second point on the peripheral edge of the concaveportion, and a first average of an absolute value of an inclinationangle of the first curve relative to the substrate surface is largerthan a second average of an absolute value of an inclination angle ofthe second curve relative to the substrate surface, and wherein thesecond vertical section is perpendicular to the first vertical sectionand has an internal shape defined by a shallow curve and deep curvesformed at both sides of the shallow curve, the deep curves having asmaller radius of curvature compared with the shallow curve.
 2. Areflector according to claim 1, wherein the concave portions are formedsuch that the first vertical sections and the second vertical sectionsof each concave portion are aligned in the same direction andorientations of the first curves in each concave portion are the same.3. A reflector according to claim 1, wherein the inclination angle ofthe first curve relative to the substrate surface and the inclinationangle of the second curve relative to the substrate surface aresubstantially zero at the point at which the first curve and the secondcurve are connected to each other.
 4. A reflector according to claim 1,wherein the concave portions are irregularly formed such that the depththereof varies in a range of about 0.1 μm to 3 μm.
 5. A reflectoraccording to claim 1, wherein the concave portions are irregularlyarranged next to each other.
 6. A reflective liquid crystal displaycomprising a reflector according to claim
 1. 7. A liquid crystal displayaccording to claim 6, wherein the concave portions are formed such thatthe first vertical sections and the second vertical sections of eachconcave portion are aligned in the same direction and orientations ofthe first curves in each concave portion are the same, and the reflectoris installed such that the first curves are disposed above the secondcurves in each concave portion when viewed by an observer.
 8. Areflector according to claim 1, wherein the deep curves are formedsymmetrically across the shallow curve.
 9. A reflector according toclaim 1, wherein the deepest points and central points of the concaveportions are not vertically aligned.
 10. A reflector according to claim1, wherein the first average varies from about 2° to 90°.
 11. Areflector according to claim 1, wherein the second average varies fromabout 1° to 89°.
 12. A reflector according to claim 1, wherein anabsolute value of an inclination angle of the shallow curve relative tothe substrate surface is at most about 10°.
 13. A reflector according toclaim 1, wherein an absolute value of an inclination angle of the deepcurve relative to the substrate surface is about 2° to 90°.
 14. Areflector in which peak reflectance is obtained at about a specularreflection angle and a first integrated value of reflectance in areflection-angle range smaller than the specular reflection angle withrespect to a substrate surface is different from a second integratedvalue of reflectance in a reflection-angle range larger than thespecular reflection angle.
 15. A reflective liquid crystal displaycomprising a reflector according to claim 14, wherein the reflector isinstalled such that the reflection-angle range corresponding to thelarger of the integrated values of reflectance is disposed at an upperside of the specular reflection angle with respect to the substratesurface when viewed by an observer.
 16. A reflector according to claim14, wherein a secondary peak in reflectance is formed in the reflectionangle range smaller than the specular reflection angle.
 17. A reflectoraccording to claim 16, wherein the secondary peak is disposed at anangle between normal to the substrate surface and about 20° from normalto the substrate surface.
 18. A reflector according to claim 14, whereinthe first integrated value of reflectance is larger than the secondintegrated value of reflectance.
 19. A reflector comprising a substratehaving a plurality of light-reflective concave portions on a surfacethereof and a peak reflectance at about a specular reflection angle anda first integrated value of reflectance in a first reflection-anglerange smaller than the specular reflection angle with respect to asubstrate surface is larger than a second integrated value ofreflectance in a second reflection-angle range larger than the specularreflection angle, the concave portions having a first vertical sectionincluding a first curve and a second curve and a second verticalsection, wherein the first curve extends from a first point on aperipheral edge of one of the concave portions to a deepest point of theone of the concave portions and the second curve extends from the firstcurve and from the deepest point of the one of the concave portions to asecond point on the peripheral edge of the one of the concave portions,and wherein a first average of an absolute value of an inclination angleof the first curve relative to the substrate surface is larger than asecond average of an absolute value of an inclination angle of thesecond curve relative to the substrate surface.
 20. A reflectoraccording to claim 19, wherein the second vertical section of the one ofthe concave portions is perpendicular to the first vertical section ofthe one of the concave portions and includes a shallow curve and deepcurves formed at both sides of the shallow curve, the deep curves havinga smaller radius of curvature than the shallow curve.
 21. A reflectiveliquid crystal display comprising a reflector according to claim 20,wherein the reflector is installed such that the first reflection-anglerange is disposed at an upper side of the specular reflection angle withrespect to the substrate surface when viewed by an observer.
 22. Areflector according to claim 20, wherein a secondary peak in reflectanceis formed in the first reflection-angle range.
 23. A reflector accordingto claim 22, wherein the secondary peak is disposed at an angle betweennormal to the substrate surface and about 20° from normal to thesubstrate surface.
 24. A reflector according to claim 20, wherein thefirst vertical sections and the second vertical sections of the concaveportions are aligned in the same direction and orientations of the firstcurves in the concave portions are the same.
 25. A reflective liquidcrystal display comprising a reflector according to claim
 20. 26. Aliquid crystal display according to claim 25, wherein the first verticalsections and the second vertical sections of the concave portions arealigned in the same direction and orientations of the first curves inthe concave portions are the same, and the reflector is installed suchthat the first curves are disposed above the second curves in eachconcave portion when viewed by an observer.
 27. A reflector according toclaim 20, wherein an absolute value of an inclination angle of theshallow curve relative to the substrate surface is at most about 10°.